Modern hospitals have implemented networks of various digital modalities such as a magnetic resonance (MR), computed tomography (CT), digital radiography, and ultrasound devices. These modalities, referred to as input imaging devices, produce vast numbers of diagnostic quality digital medical images. In order to more easily manage such images many hospitals are implementing a network of specialized equipment and components designed to support medical radiological imaging commonly referred to as a Picture Archiving and Communicating System (PACS). A PACS allows a radiologist to easily manage the large volume of digital medical images including archiving, retrieving, exchanging, displaying and manipulating images and associated reports. For example, when a patient is imaged by a medical modality, a series of digital images, referred to as a “series”, is generated, captured and archived. A radiologist typically dictates a report that is later transcribed into some type of text document. A radiologist can easily and quickly retrieve the patient's series, or any previous series, and display the series on a display station for viewing. Furthermore, the retrieved study or series can be forwarded to another radiologist, perhaps located at a remote hospital. By easing the burden of managing digital medical images, PACS are expected to improve patient care and the efficiency of the radiology department. Furthermore, by integrating PACS with a Hospital Information Management System (HIS), patient information can be coupled with the study, thereby improving the efficiency of the hospital as a whole.
In order to facilitate archival and retrieval of medical images, a PACS typically incorporates a short-term storage device having a plurality of short-term storage media, such as RAID, NAS, OR SAN, which are typically rewritable media, and a long-term storage device having a plurality of long-term storage media, such as a tape or optical device archiving device capable of managing an automated or manual library of volumes. As new images and associated reports are generated from the various medical modalities, the system stores the images on the short-term storage device using a “best-fit” approach. In this manner, the system distributes the images across the plurality of short-term storage media in order to minimize wasted storage space. Thus, each image in a patient's series may be stored on unique media in order to most efficiently manage storage space. A central database maintains the location of each image. If a radiologist does not request a patient's series for a period of time, the system automatically moves the corresponding images to the long-term (near-line) storage device and updates the database. The PACS distributes the images of the series across the long-term storage media to minimize wasted storage space. When, for example, a radiologist or a radiology technician (i.e., a user) requests a particular patient's series, the system accesses the database to determine the current location of the patient's images and reports. If the desired images reside on long-term storage media within the long-term storage device, the PACS automatically retrieves the images and moves them to the short-term storage device.
Although the best-fit archival scheme typically used by a PACS provides the benefits discussed above, it also has many shortcomings. For example, because the best-fit method distributes images across a plurality of media, it does not readily allow patient records to be physically archived to a shelf or an off-site storage facility. When a radiologist requests images for a particular patient, the hospital staff may have to physically retrieve several media from archive. Even if all the necessary long-term storage media is currently loaded into the long-term storage device, the device must independently initialize each long-term storage medium for access. Thus, in certain scenarios, the best-fit method can greatly increase archive retrieval time, thus compromising the efficiency of the archival system and increasing the cost thereof. For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need for a digital image management system which reduces access time and which requires less intervention by system administrators.